effectiveness of crude extract and purified protein from ... · explores on use of purified seed...

INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 4, No 3, 2013

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4402

Received on September 2013 Published on November 2013 259

Effectiveness of crude extract and purified protein from Vigna unguiculata

seed in purification of charco dam water for drinking in Tanzania Nancy Jotham Marobhe

School of Environmental Science and Technology (SEST), Ardhi University (ARU)

P.O Box 35176, Dar es Salaam, Tanzania

[email protected]

doi:10.6088/ijes.2013040300005

ABSTRACT

Due to chronic water supply problems prevailing in most rural areas of Tanzania, households

are obliged to use man made water reservoirs (charco dams) for drinking after receiving

inadequate treatment using powdered seeds from different plant species. This study is aimed

at investigating the capacity of crude extract and purified proteins (coagulant proteins) from

Vigna unguiculata (VUP) seed to purify drinking water from Nunguru charco dam.

Coagulant proteins were purified from V. unguiculata crude seed extract (VUCE) by

modified ion exchange chromatography technique. The VUP were found to be cationic in

nature and have the molecular mass of about 6 kDa, which is very similar to the coagulant

proteins purified from Moringa oleifera and Parkinsonia aculeata seeds. The coagulation

potentials of VUP and VUCE were verified by jar experiments and the performances were

compared to those of aluminium sulphate (alum) using water samples with initial turbidity of

880 NTU. The coagulant proteins reduced most pollutants to the levels that complied with the

Tanzania Drinking Water Standards and WHO standards. Minimum residual turbidity

achieved by both VUCE and VUP was 3 NTU and 12 NTU for alum. The VUP performed

best at the dosage of 8 mg/L which was almost ten times lower than that observed for VUCE

(76 mg/L). The VUP reduced organic load in treated water by 80% while VUCE increased it

by almost 100%. Although the VUP and VUCE did not alter the pH and alkalinity of the

treated water, the VUP increased the conductivity of water substantially without affecting the

water palatability. The VUP and VUCE reduced Fe2+ in coagulated by 93 - 98% while NO3-

and PO43- were reduced by 91 – 99% and 94 - 99.6%, respectively. The VUP and alum

reduced fecal indicators by 94 and 98.6% respectively. The purification procedure of

coagulant proteins is simple and user friendly and hence it could be scaled up for large scale

production of coagulant proteins for use in water treatment processes in Tanzania. The VUCE

and VUP are recommended for production of drinking water and other domestic uses so as to

reduce the incidences of cholera and improve people’s health and hygiene.

Keywords: Cation exchanger, coagulant seed proteins, turbid water, rural areas.

1. Introduction

Drinking water sources contaminated by intestinal pathogens including inorganic and organic

pollutants are responsible for various health hazards in many poor countries (Wilson and

Andrews, 2011; Pokhrel and Viraraghavan, 2004). The removal of turbidity during water

treatment process in inevitable since suspended particles are media for transmission of harmful

organic and inorganic contaminants, taste, odor and color– producing compounds and

pathogenic organisms (Raghuwanshi et al., 2002). Safe water supply coverage in Tanzania is

still very low whereby less than 73% and 50 % of urban and rural population respectively, have

Effectiveness of crude extract and purified protein from Vigna unguiculata seed in purification of charco dam

water for drinking in Tanzania

Nancy Jotham Marobhe

International Journal of Environmental Sciences Volume 4 No.3, 2013 260

access to safe water supply. Due to chronic shortage of clean drinking water supply in most

rural areas of Tanzania, the Government of Tanzania and development partners have opted to

invest in construction of charco dams (man-made reservoirs) as one of the reliable sources of

water supply that will cater for both human and animal’s needs throughout the year (URT,

2002).

Production of clean and safe water from most raw water sources necessitates application of

coagulation-flocculation process to remove turbidity in the form of suspended and colloidal

matter. Although aluminium salts (e.g. Al2(SO4)3.18H2O) and synthetic organic polymers are

the most widely used coagulants in water treatment works, cost implications and deleterious

environmental effect of these chemicals has triggered interest in research for plant seeds that

could act as natural coagulants (Katayon et al, 2005).

Coagulation of turbid surface water sources in rural areas of Tanzania like in many other

developing countries is done at a household level using plant materials (Jahn, 1984; Al-Samawi

and Shokralla, 1996; Leite, 2007). The seed powder of Vigna unguiculata is among the natural

coagulants that are widely used for purification of water fetched from charco dams and rivers in

rural areas of Tanzania. Studies conducted by Marobhe et al. (2007a) on effectiveness of crude

extract of V. unguiculata seeds on removal of river and synthetic water turbidities under varied

operating parameters revealed that, the seeds possess high coagulating potential. Several

detailed research papers have been published on the performance of natural coagulants of

which, Moringa oleifera has been studied extensively (Okuda et al., 2001; Ghebremichael et

al., 2005; Arnoldsson et al., 2008). It has been observed that the main disadvantage of using

crude seed extracts in water treatment is the increased chemical oxygen demand (COD) in the

treated water due to organic nature of such extracts and hence it enhances deterioration of

treated water upon storage for prolonged period of time (Ndabigengesere and Narasiah, 1998;

Arnoldsson et al., 2008). Thus, the aim of this study was to investigate into the effect of crude

extract of V. unguiculata seed (VUCE) and coagulant proteins purified from the crude extract

of VUCE on various physical, chemical and microbiological quality parameters in the treated

charco dam water. To the best of my knowledge, this is the first intensive investigation that

explores on use of purified seed proteins of V. unguiculata plant for purification of charco dam

water for drinking and other domestic purposes.

2. Material and methods

2.1 Source of V. unguiculata seeds and charco dam water samples

V. unguiculata seeds used as natural coagulant in this study were obtained from Singida rural

district in central parts of Tanzania. The dry pods of V. unguiculata were collected from rural

households and transported to the Applied Environmental Microbiology laboratory at the Royal

Institute of Technology (KTH), Sweden, for purification of coagulating protein. Coagulation-

flocculation experiments to remove suspended particles including fecal indicator bacteria in

charco dam were conducted at the laboratory of microbiology and technology at Ardhi

University, Tanzania using coagulating proteins purified in Sweden. Water samples were

collected from Nunguru charco dam in Singida rural district, Tanzania during dry season.

Approximately, 10 l of water samples were collected in plastic buckets and transported to the

Environmental engineering analytical laboratory at Ardhi University for experimental analysis.

Water samples for bacteriological analysis were collected in sterile one liter glass bottles and

transported to the Singida district water laboratory for analysis.





2.2 Preparation of crude seed extracts and purification of coagulant protein

The V. unguiculata crude seed extract (VUCE) was prepared as five percent (5%, W/W)

solution from the fine seed powder in distilled water as detailed by Marobhe et al. (2007b).

The quality parameters of VUCE were analyzed according to the procedure detailed in the

Standard Methods for the examination of Water and Wastewater (APHA et al., 1998).

Coagulant proteins were purified from the VUCE using a cation exchange resin followed by

elution of bound proteins using 0.3 and 0.6 M sodium chloride (NaCl) as detailed by

Marobhe et al. (2013) for purification of Parkinsonia aculeata coagulant proteins. The eluted

proteins from the cation exchanger resin were termed V. unguiculata pure proteins or simply

VUP. Protein concentration in samples collected during the purification process was

measured using dye binding method (Bradford, 1976). Protein samples that were eluted with

0.6 M NaCl were used in all coagulation experiments to study the quality of water treated

with the proteins due higher amount of proteins eluted than that when 0.3M NaCl was used.

For comparison purposes, alum was also prepared as 5% solution (W/V), while the coagulant

protein purified from Moringa oleifera (MOCP) was provided by the Department of

Environmental Microbiology at KTH, Sweden. The Sodium Dodecyl Sulphate-

Polyacrylamide Gel Electrophoresis (SDS-PAGE) to check the purity and molecular masses

of the VUP was carried as detailed by (Hultmark et al., 1983; Ghebremichael et al. 2006).

2.3 Coagulation experiments and water quality analysis

2.3.1 Coagulation experiments

The jar tester apparatus (Model, Phipps and Bird – PB-700TM) was used in coagulation-

flocculation experiments whereby different dosages of VUCE, VUP and alum were added into

six different beakers each containing one liter of water samples. The intensity and duration of

rapid and slow mixing including settling time of coagulated water samples were set as detailed

by Marobhe and Gunno (2013).

2.3.2 Measurement of water quality and analytical methods

The quality of water sample coagulated with both natural and chemical coagulants was

examined using the methods stated in the Standard Methods for the Examination of Water

and Wastewater (APHA et al., 1998). The physical and chemical water quality parameters

that were analyzed included turbidity, pH, Total Dissolved Solids (TDS), conductivity,

salinity, alkalinity, cation concentration (Fe2+), and anion concentration (NO3-, PO4

3- and

SO42-) and organic compounds measured as COD as described earlier by Marobhe and Gunno

(2013) for P. aculeata coagulant protein. The turbidity was measured using a 2100 P

turbidimeter from Hach Company. The density of fecal coliforms (FC) and other coliform

bacteria in the raw and treated water samples were enumerated using Standard Method 9221E

Faecal Coliform Membrane Filter Procedure (APHA, et al., 1998) after 30 min of settling

time of coagulated water.

3. Results

3.1 Water quality in charco dams

Table 1 presents the typical turbidity and pH levels in selected charco dams located in

Singida rural district in central parts of Tanzania. The results revealed that, charco dams have

very high turbidities, in which, during dry and rain seasons the turbidity ranged from 1570 to





4300 NTU and 550 to 400 NTU respectively. The pH level in the charco dams during both

dry and rain season range from 6.9 and 7.5. Also, Table 2 shows the average, range and

standard deviation of raw water quality parameters of Nunguru charco dam based on three

analyses. It is evident that Nunguru dam is very turbid (730 - 900 NTU) and also, it contains

high concentration of iron (Fe2+) (23.8-31.5 mgl-1), which makes it objectionable for drinking

without treatment.

Table 1: Physical quality and capacity of selected charco dams

Reservoir/

charco dam name

Estimated

volume (m3)

Average turbidity (NTU)

Average pH

dry season rain

season

dry

season

rain

season

Nunguru 280,000 2790 550 7.1 7.5

Mipilo 89,000 4300 780 7 7.3

Ngororijanda 36,400 1570 520 7.1 7.2

Suke 570,700 1900 450 6.9 7.2

Sagara 573,600 1590 430 7 7.4

Ikungi 190,000 1980 400 7.2 7.4

Ikomesi 197,400 2680 590 6.9 7.2

Table 2: Representative water quality parameters of Nunguru charco dam

Parameter Average Range STDEV

pH 7.4 7.2- 7.5 ± 0.17

0.173205

Turbidity (NTU)

810 730-900 ± 85.4

Total Dissolved Solids (TDS) (mg/L)

)

37.8 33.5-41 ± 3.9

Electrical conductivity (µs/cm) 72.9 69.7-80 ± 72.9

Alkalinity (as CaCO3) (mg/L)

)

74 68.6-80 ± 5.72

Iron (mg/L)

)

27 23.8-31.5 ± 4

Chloride (mg/L)

120 99 -136 ± 19

Nitrate –N (mg/L)

)

33 27-43 ± 7.9

Phosphate (mg/L)

)

9 6.6-12.4 ± 3.03

Chemical Oxygen Demand 80 75-87 ± 6.24

(COD) (mg/L)

3.2 Purified coagulant seed protein for coagulation of charco dam water samples

Table 3 shows the average values of selected quality parameters of VUCE and VUP eluted by

0.6 M NaCl based on two analyses. The VUCE contains more organic matter expressed as

Chemical Oxygen Demand (COD) (8,700 mg/L) and protein content (1,280 mg/L) than in

VUP samples which contained 920 of COD and 440 mg/L of proteins. Also, the VUP

samples had the conductivity of 32,400 µs/cm which is much higher than that in the VUCE

samples (233 µs/cm).





Table 3: Physico-chemical characteristics of crude seed extract and purified coagulant

proteins

Parameter Units VUCE VUP (0.6 M NaCl

eluted) pH

6.57 6.4

Total Dissolved Solids (TDS) mg/L

118.6 16,400

Conductivity µs/cm 233 32,400

Salinity

ppt 0.1 4.8

Alkalinity (as CaCO3)

mg/L

80 20

Iron (Fe2+)

mg/L 0.66 0

Nitrate (NO3-)

mg/L 10.5 0

Phosphate (PO4-2)

mg/L 17 0

Protein content mg/L 1280 440

Chemical Oxygen Demand (COD) mg/L 8,700 920

Note. VUCE and VUP are abbreviations for V. unguiculata crude extract (VUCE) and

purified proteins (VUP) eluted by 0.6 M NaCl, respectively.

The results for SDS-PAGE of coagulant proteins at different stages of purification starting

with VUCE, unbound proteins, VUP and MOCP (as a reference) are displayed in Figure 1.

The results showed that the bound proteins of VU were eluted in pure state as indicated by

thick single bands situated in the region of about 6 kDa, which is very similar to the

molecular weight of the MOCP and that of P. aculeata coagulant protein (PAP) reported by

Marobhe and Gunno (2013).

Figure 1: SDS – PAGE of V. unguiculata proteins at various stages of coagulant protein

purification. Lane 1 shows marker protein with molecular masses of 4 – 148; Lane 2

represents purified protein of M. oleifera; Lane 3 crude seed extract; Lane 4 and 5 shows

unbound proteins and Lane 6 and 7 represents proteins eluted by 0.3 M and 0.6 M NaCl

respectively.





3.3 Effect of coagulants on the quality of treated water samples

Coagulation-flocculation experiments were run in triplicate and the results were highly

reproducible. The results of the quality of water coagulated with purified coagulant proteins

after 30 min of sedimentation are shown in Figure 2 through 6. Standard deviations from three

analyses were computed and indicated in graphs as vertical lines.

3.3.1 Turbidity and chemical oxygen demand

The effects of varying the dosages of VUCE, VUP and alum on turbidity and COD of the

treated water are presented in Figure 2a and b, respectively. The results showed that the

reduction of turbidity increased with increasing the dosage of VUCE, VUP and alum until the

optimal dosages for the maximum turbidity removal was ensued. Figure 2a shows that the

optimal dosage for VUCE was 76 mg/L which reduced turbidity from 880 NTU at zero dosage

to 3 NTU. Also, the results showed that, at the optimal coagulation dosage of the VUCE, the

COD increased from 80 in raw water to 182 mg/L in treated water which suggests that, most of

organic component in the VUCE (Table 1) flocculated and settled along with other particulate

matter in the water. Similarly, Fig. 2b shows that the minimum residual turbidity of 3 and 12

NTU were attained after coagulation with 8 and 14 mg/L of VUP and alum, which correspond

to turbidity removal efficiencies of 99.7% and 98.6% respectively. Likewise, the COD of the

treated water dropped from 80 mg/L at zero dosage of coagulants to 20 and 15 at optimal

coagulation dosages of VUP and alum, respectively.

0

50

100

150

200

250

300

350

400

450

0

100

200

300

400

500

600

700

800

900

1000

0 20 40 60 80 100

CO

D (

mg/

L)

Res

idua

l tu

rbid

ity

(NT

U)

Dosage of coagulants (mg/L)

VUCE (turbidity)

VUCE (COD)

Figure 2a: The effect of different dosages of crude seed extract (VUCE) on turbidity and COD

levels in the treated water.





Figure 2b: The effect of different dosages of purified coagulant protein (VUP) and ALUM

on turbidity and COD levels in the treated water.

3.3.2 Effect on pH and alkalinity

The pH and alkalinity levels in water treated by different dosages of VUCE, VUP and alum are

shown in Figure 3a and b. It is deduced from the results that the water treated with VUCE and

VUP demonstrates insignificant variation in pH and alkalinity levels.

The results depicted that the pH of treated water remained more or less constant between pH

7.2 and 7.4 while the values for alkalinity ranged from 50 to 55 mg/L (as CaCO3) throughout

the range of dosages tested. Unlike coagulant proteins, the pH and alkalinity of water treated

with alum dropped from 7.4 to 4.3 and 70.7 to 3 mg/L (as CaCO3) respectively (Figure 3b).

Figure 3a: The effect of variation of dosages of crude seed extracts (VUCE) on pH and

alkalinity of treated water.





Figure 3b: Effect of variation of the dosages of purified coagulant proteins (VUP) on pH and

alkalinity of treated water in comparison with alum.

3.3.3 Electrical conductivity

The conductivity data of water treated with different dosages of VUCE, VUP and alum are

presented in Figure 4a and 4b. Figure 4a shows that at optimal coagulation dosage of VUCE

(76 mg l-1), the electrical conductivity in the water increased from 75 µs cm-1 at zero dosage to

92 µs cm-1 (22% increase) after treatment. Moreover, minor variations in water electrical

conductivity were seen at dosages above those optimal for turbidity removal. The observed

conductivity values in the treated water are however; lower than those observed in the VUCE

(Ref. Table 1). The results shown in Figure 4b revealed that unlike VUCE, the electrical

conductivity of the water treated with VUP increased considerably with increase of the dosage

of VUP and alum. At the optimum dosages for turbidity removal of VUP (8 mg l-1) and alum

(14 mg l-1), the electrical conductivity increased from 74 µs cm-1 of raw water to 713 and 1270

µs cm-1 respectively. This is due to incorporation of Cl- into the water from sodium chloride

used for protein purification and SO42- from alum used in coagulation process.

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Con

duct

ivit

y (µ

s/cm

)

Dosage of VUCE (mg/L)

VUCE

Raw water (untreated)

Figure 4a: Conductivity of water treated with different dosages of crude seed extract (VUCE).





0

200

400

600

800

1000

1200

1400

1600

0 2 4 6 8 10 12 14 16

Cond

uctiv

ity

(µS

/cm

)


VUP

ALUM

Figure 4b: Conductivity of water treated with different dosages of purified coagulant

proteins (VUP) and alum.

3.3.4 Iron and nutrients concentration

The change in concentration of Fe2+, NO3- and PO4

3- in water after treatment with VUCE, VUP

and alum is shown in Figure: 5a and b. It was observed that the concentration of Fe2+, NO3- and

PO43- in the treated water decreased with the increase of dosage of VUCE, VUP and alum. The

concentrations of Fe2+, NO3- and PO4

3- at zero dosage of coagulants were 21.1, 33.3 and 7.5

mg/L respectively. The concentrations of Fe2+, NO3- and PO4

3- at optimal dosage of VUCE for

turbidity removal including the removal efficiencies in parentheses were 0.39 (98.1%) 0.14

(99.6%) and 0.42 (94.4%) mg l-1. Moreover, the results in Figure 5b showed that the

concentration of Fe2+, NO3- and PO4

3- in water treated with optimum dosage of VUP for

turbidity removal were 1.4, 3 and 1.4 mg/L which correspond to the removal efficiencies of

93.4, 91 and 81.6% respectively. However, much lower concentrations of pollutants in the

treated were observed at the protein dosage slightly higher than those required for turbidity

removal. Similarly, the removal efficiencies of 46, 95.5 and 96% respectively, were observed

for Fe2+, NO3- and PO4

3- in water treated with optimal dosage of alum for turbidity removal.

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120

Con

cent

ratio

n (m

g/L

)


VUCE (ferrous ion)

VUCE (phosphate)

VUCE (nitrate)





Figure 5a: The effect of varying the dosages of crude seed extracts (VUCE) and on

concentration of ferrous, nitrate and phosphate ions in the treated water.

Figure 5b: The effect of varying the dosages of purified coagulant protein (VUP) and alum

on concentration of ferrous, nitrate and phosphate ions in the treated water.

3.3.5 Indicators of fecal pollution (Coliforms)

The counts of total and fecal coliforms before and after water coagulation are shown in Figure

6. The untreated charco dam water had an average total coliforms density of 4x104/ml and

2.3x103/ml of fecal coliforms. Un-coagulated water removed between 24.8% and 26.4% of

total coliforms and fecal coliforms, respectively, by plain sedimentation. The removal

efficiencies of total coliforms and fecal coliforms by VUP were 95% and 94% respectively,

whereas for alum were 98.7 and 98.6% respectively. The results also revealed that, the optimal

dosages for bacterial removal were similar to those observed for turbidity removal.

Figure 6: The effect of purified coagulant protein (VUP) and alum on fecal indicator bacteria

in the water coagulated with different dosages of coagulants.





4. Discussion

There is scientific evidence that, interventions targeted at poor populations could provide

significant health benefits and contribute to poverty alleviation (Gundry et al., 2004).

Since water in charco dams is highly polluted with particulate matter and inorganic pollutants

especially iron (Table 1 and 2), purification of the water prior drinking and other domestic

uses is unavoidable. This will be possible by appraisal of existing natural and/or traditional

water coagulation methods through scientific investigations. It is anticipated that, the natural

water coagulation technology will not only benefit the rural populations but also, the urban

water utilities, which often distribute insufficiently treated water to consumers due to

inadequate resources at water treatment plants.

Purification of coagulant proteins from VUCE using ion exchanger chromatography has

verified that the VUP have very similar characteristics to coagulant proteins purified from

other types of seeds. The electrophoretic pattern of VUP was found to be very similar to that

of the reference coagulant protein from Moringa seed (MOP), which was also reported

previously by Ghebremichael et al. (2006) as well as to that observed for P. aculeata

coagulant protein (PAP) (Marobhe and Gunno, 2013). Such homologies among coagulant

proteins may form the basis for explaining the coagulation potential of other seeds that have

been traditionally used in water clarification in different rural areas of Tanzania (Marobhe et

al., 2007b). However, it is possible that VUP, PAP, MOP and other coagulant proteins might

have variations in other characteristics especially the polypeptide sequences. Past studies

done by Marobhe et al. (2007b) have revealed that VUP and PAP either as a protein

concentrate or powder (lyophilized protein) are stable and could be stored easily at different

conditions. It is apparent that a single elution step using 0.6 M NaCl is sufficient to remove

most non-coagulating proteins from VUCE to produce a sample rich in active coagulating

proteins. Since the main drawback of VUCE is the addition of organic and inorganic matter

into treated water, application of purified proteins will circumvent the problems associated

with VUCE. Due to consistency of charco dam water, the VUCE could help rural households

to produce drinking water although coagulant dosage needs to be carefully controlled so as to

reach optimum destabilization. The dosages (seed powder) applied by households in rural

areas of Tanzania to clarify water fetched from charco dams is extremely high (up to 125

times higher than the optimum dosage of VUCE that has been established in this work).

Excessive dosages of natural coagulants are associated with fast deterioration of treated water

due to regrowth of residual bacteria upon storage at room temperature (Marobhe et al., 2007a;

Wilson et al., 2011).

With respect to water purification, both the VUCE and VUP purified water from the charco

dam to the level that complied with the Tanzania Drinking Water Quality Standard (TDWS) of

30 NTU and World Health Organization (WHO) standard of 5 NTU. Maximum turbidity

removal of VUP was achieved at the dosage about ten times lower than that required for the

VUCE. Also, water coagulation using VUP reduced up to 80% COD in the treated water, while

VUCE increased the COD by almost 100%. Coagulation of turbid water using minimum

dosage of VUCE for maximum turbidity removal will prolong the storage time of the treated

water and also will help households in rural areas to save the seeds for food and other uses.

However, further studies to ascertain the cost implications and shelf life of surface water

samples treated using crude seed extracts and purified proteins are necessary.

Unlike alum, coagulation of charco dam water using VUCE and VUP did not affect the pH and

alkalinity of the treated water. The pH values of treated water were within the pH range





acceptable for drinking water which is 6.5 to 8.5 (WHO, 1996). The propensity of alum to

reduce the pH of water during coagulation process has been reported by Martyn et al. (1989).

These results suggest that, coagulant proteins possess natural buffering property that avoids the

need for application of lime or bicarbonate to raise the pH and hence, it reduces the cost for

water treatment. Although the VUP increased the conductivity of the treated water

significantly, the water retained its palatability. However, elution of proteins using low

concentration of salt solution could be advantageous. Similar to VUCE, the crude extract of M.

oleifera seed also did not have a significant effect on conductivity of treated water

(Ghebremichael at el., 2006; Ndabigengesere and Narasiah, 1998).

The removal of Fe2+, NO3- and PO4

3- in water after coagulation with VUCE and VUP was

substantial and the residual ions conformed to the TDWS set at 1 mg l-1, 10 mg/L and 30

mg/L respectively. Similarly, the removal of up to 92.1% and 89.6% of Fe2+ in wastewater

and charco dam coagulated by Moringa seed powder and PAP respectively, has been

reported by Sajidu et al. (2005) and (Marobhe and Gunno, 2013). The results also support

previous observations, which showed that a lower turbidity of treated water is an indicator of

more efficient removal of organic and inorganic contaminants associated with particulate

matter (Kavanaugh et al., 1978). The removal of PO43- and perhaps other ions could be due to

aeration and adsorption of ions onto large flocs of colloidal particles that settled along with

flocs (Özacar and Sengil, 2003). As shown in Table 2 and 3, water from charco dams is very

turbid and contains high concentration of Fe2+, which causes the water to be reddish brown in

color. The removal of Fe2+ from water is necessary not only for health reasons but also for its

effects on laundry. The water from Nunguru dam treated with VUCE and VUP were very

clear and appealing for drinking. The removal of NO3- in drinking water limits the risk of

gastric cancer (Yang et al., 1998) and methaemoglobinaemia in infants, which is otherwise

widely spread in rural areas of Tanzania.

The prevalence of many waterborne diseases, especially cholera, typhoid and bacillary

dysentery in many rural areas of Tanzania is due to consumption of untreated or partially

treated charco dam water at household levels. Water coagulation using VUP and alum

decreased considerably the counts of fecal coliforms in the clarified water. The performance

of alum in bacterial removal surpassed the VUP because of the propensity of alum to

remarkably reduce the pH of water, which is lethal for most of the bacteria. The effectiveness

of coagulants proteins on turbidity and bacterial removal may render these natural materials

suitable for simultaneous coagulation and disinfection of turbid surface waters for rural and

peri-urban populations in developing countries. However, post treatment of the water

clarified by coagulant proteins using natural materials reported by Dalsgaard et al. (1997);

Clasen and Bastable, 2003; Sarah et al., 2011) to destroy residual bacteria prior drinking is

necessary.

The natural coagulation technology is one of several environmentally friendly interventions,

which could help rural and semi-urban populations to produce clean drinking water and provide

a means of combating poverty (Sajidu et al., 2005; Gundry et al., 2004).

The cost for production of coagulant proteins will be low compared to conventional methods

for purification of proteins, which requires special equipment, reagents and trained personnel.

About 2900 mg of proteins could be purified from 7g of V. unguiculata and about 6200 mg

VUP can purify 1 m3 of turbid water. Therefore, approximately less than 1.5 USD will be

enough to treat about 1 m3 of high turbid water using VUP. Supplementing or replacing

chemical coagulants with coagulant proteins will be suitable for agro-based developing





countries such as Tanzania because large scale production of these coagulants could improve

the socio-economic conditions of people.

5. Conclusion

From the present study, it may be concluded that, water in charco dams is highly polluted and

hence proper treatment through appraisal of traditional water coagulation methods is needed.

Coagulation-flocculation and sedimentation of charco dam water samples with V. unguiculata

crude seed extracts (VUCE) and coagulant proteins purified from VUCE (VUP) removed

suspended matter and most other pollutants to the levels that complied with Tanzanian

Drinking Water Standards and WHO for drinking water.

More specifically:

1. The turbidity removal efficiencies of VUP, VUCE and alum differed very slightly.

The lowest turbidities at optimum dosages of both VUP, VUCE was 3 NTU while

the observed minimum turbidity for alum was 12 NTU, which, corresponded to the

removal efficiency of to 99.7 and 98.6% respectively. The optimal coagulation

dosage of VUP was about ten times lower than those of VUCE.

2. The VUP reduced organic load in treated water by 80% which makeit possible to

store the treated water for long periods without deterioration.

3. Unlike alum, the VUCE and VUP had no significant effect on pH and alkalinity of

the treated water. This avoids the need for additives for regulating the pH and

alkalinity of water treated natural coagulants.

4. The VUCE and VUP reduced significant amounts of Fe2+, NO3- and PO4

3- from

treated water. The aesthetic quality of charco dam water treated with coagulants

improved significantly due to the removal of substantial amounts of ferrous ions.

5. The coagulant proteins reduced up to 94% of fecal coliforms in coagulated water

after 30 min of settling time. Additional natural disinfection of coagulated water to

remove pathogens is necessary before the water is drunk.

6. The protein purification technique used here is simple and rapid and can be easily

scaled up for production of large quantities of coagulant protein for households and

water treatment plants applications. The VUCE is recommended for household

water treatment but careful control of coagulant dosage is needed to give optimum

coagulation.

Acknowledgements

I acknowledge the financial support provided by Sida-SAREC. I appreciate the assistance

extended by Mr. Mbulume. R and Mr. Ndimbo during laboratory work. My thanks also goes to

the Department of Environmental Microbiology at the Royal Institute of Technology (KTH),

Sweden for the facilities used during protein purification. I also thank Prof. Gunno Renman for

the fruitful discussions and inputs.

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